Azido-pyridazones



United States Patent 4 Claims. (61. 260-250) This application is adivisional application of our copending application Serial No. 382,411,filed July 13, 1964, which in turn is a continuation-in-part of ourapplication Serial No. 234,238, filed October 30, 1962, now US. PatentNo. 3,157,646.

It is known to use pyridazone derivatives to influence plant growth.Known compounds for this purpose have the disadvantage, however, that aconsiderable period elapses after their use before their effect becomesevident.

We have now found that agents which contain a pyridazone of the generalformula:

in which X denotes a halogen atom, especially a chlorine atom, R denotesa substituted or unsubstituted alkyl, phenyl or cycloalkyl radicalespecially cyclohexyl, and R is azido, are free from the saiddisadvantage.

The agents according to this invention have the advantage that they canmore easily be emulsified in water than known agents.

The agents have good selectivity in respect of weeds among cultivatedplants, for example onions or sugar beet, and take efiect rapidly, i.e.,only a short time after their use. Furthermore their after-effect in thesoil is of short duration. Rapid crop rotation is therefore possible.The agents according to this invention may also be used in suitabledosage for the total destruction or inhibition of undesired plantgrowth. For this purpose they may be used in amounts of about 1 to kg.of active ingredient per hectare.

Agents according to this invention may furthermore be used to achieveother influences on plant growth, especially for dehydration,acceleration of ripening by premature desiccation, for example in potatocrops, and also for reducing fruit setting, retarding blossoming, andprolonging the harvest period and storage life.

The agents according to this invention may also be used in suitableconcentrations as shoot promoting and root promoting agents.

The new pyridazone derivatives to be used according to this inventionmay be prepared by methods analogous to conventional methods. Forexample, reaction of 1- 3,210,354 Patented Oct. 5, 1965phenyl-4,S-dichloropyridazone (or the l-lower alkyl or1-cycloalkyl-4,S-dichloropyridazone) with sodium azide according to thegeneral reaction described by Theodor Curtius, Berichte der deutschenchemischen Gesellschatt, 55, 1564 (1922), in a suitable solvent, e.g.,alcohols, in particular ethanol, dimethylformamide or dimethylsulfoxide,yields 1 phenyl -'4-azido-S-chloropyridazone-(6) (melting point to 111C.) or the corresponding 1- lower alkyl or l-cycloalkyl compound.Analogous reaction of said dichloropyridazones with hydrazine hydrateaccording to the general reaction described by E. Meyer, Berichte derdeutschen chemischen Gesellschaft, 33, 1885 (1900), in a suitablesolvent, e.g., alcohols, in particular ethanol, dimethylformamide ordimethylsulfoxide, yields the1-phenyl-4-hydrazino-5-chloropyridazone-(6) (melting point 172 C. withdecomposition) or the corresponding l-lower alkyl or l-cycloalkylcompound. The aforesaid hydrazino compounds yield with nitrous acid in asuitable solvent, e.g., and aqueous acid solution, e.g., dilutehydrochloric acid or dilute sulfuric acid the corresponding azideaccording to the general reaction described by Theodor Curtius, Berichteder deutschen chemical Gesellschaft, 23, 3029 (1890). The abovecompounds may be used as herbicides in the form of the hydrochloride orhydrobromide salts.

A typical preparation of 1-phenyl-4-azido-5-chloropyridazone-(6) or thecorresponding 1-methyl or 1- cyclohexly compound is the reaction ofsodium azide in aqueous solution with l-phenyl (or l-methyl orl-cyclohexyl) -4,5-dichloro-pyridazone-(6) in alcohols, in particularethanol, dimethyl-formarnide or dimethylsulfoxide at about 60 to 70 C.

Another typical preparation is the reaction of nitrous acid with thel-phenyl (or l-methyl or 1-cyclohexyl)-4-hydrazino-S-chloropyridazone-(6) at about 20 to 30 C. in an aqueous acidsolution, e.g., dilute hydrochloric acid or dilute sulfuric acid. Thehydrazino compound may be derived from the aforesaid4,5-dichloropyridazone-(6) by reaction with hydrazine hydrate at about60 C. in alcohols, in particular ethanol, dimethylformamide ordimethylsulfoxide.

A typical preparation of 1-phenyl-4-hydrazino-5- chloropyridazone-(6) orthe corresponding l-methyl or l-cyclohexyl compound is the reaction ofhydrazine hydrate with l-phenyl (or l-methyl or 1-cyclohexyl)-4,5-dichloropyridazone-(6) in alcohols, in particular ethanol,dimethylformamide or dimethylsulfoxide at about 60 C.

The following is a compound according to this invention:1-pheny1-4-azido 5 chloropyridazone melting point 110 to 111 C.

The invention is illustrated by, but not limited to, the followingexample.

Example Soil is treated at the rate of 3 and 5 kg. per hectare with N [4(1 phenyl-5-chloropyridazone-(6)-yl-]N'- dimethylformamidine. The activesubstance is sprayed on the soil as an aqueous dispersion which has beenprepared with an addition of a dispersing agent (sodium ligninsulfonate). Seeds of Simzpis alba (mustard), Avena fatua (wild oats),Poa annua (rye grass), Beta vulgaris (sugar beet), Galium aparine(cleavers), Allium cepa (onion), Daucus carota (carrots) are shown inthe soil thus pretreated. At first the plants develop normally.

Six days later most of the plants begin to blanch from the tips of theleaves. After another three weeks, Sinapis alba, Avena fatua, Poa annua,and Galium wparine are practically completely withered. Beta vulgarisshows no damage whereas Allium cepa is only slightly bleached at theleaf tips.

3 4 Salts of the above forrnarnidine, and also I-phenyl-4- wherein, insaid formula, R represents a member selectedazido-S-chloro-pyridazone-(6) have a similar action. from the groupconsisting of lower alkyl, phenyl and cyclo- What We claim is: hexyl,and R is azido. 1. A compound selected from the group consisting of 2.1-phenyl-4-azido-5-chloropyridazone-(6). a compound having the formula 53. 1-methyl-4-azido-5-ch1oropyridazone-(6).

R2 4. 1-cycloheXyl-4-azido-5-chloropyridaz0ne-(6).

No references cited. 1310/ \CC1 10 NICHOLAS S. RIZZO, Primary Examiner.

1. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF A COMPOUND HAVINGTHE FORMULA 1-R1,4-R2,5-(CL-),6-(O=)-1,6-DIHYDRO-PYRIDAZINE WHEREIN, INSAID FORMULA, R1 REPRESENTS A MEMBER SELECTED FROM THE GROUP CONSISTINGOF LOWER ALKYL, PHENYL AND CYCLOHEXYL, AND R2 IS AZIDO.